Conventionally, digital multifunctional devices are available in the market for electronically scanning a document image by a scanner and outputting the image data transmitted from the scanner through a printer. Recently, improved digital multifunctional devices have appeared, equipped with a communication function (including a facsimile function and a printer function) to transmit and receive image data through communication with external devices. Further, the improved digital multifunctional devices are equipped with memories for temporarily storing the image data to be processed, so as to process large amounts of image data and multiple jobs efficiently.
On the other hand, there are various types of memories or storage devices for storing the image data, including hard disk devices using magnetic recording medium, and semiconductor memories. Such various memories have different environments for storing the image data, such as the memory capacity, cost, writing speed, readout speed, and whether it is volatile or nonvolatile.
Especially in a memory utilizing a magnetic recording medium such as a hard disk device, the disk (recording medium) is divided into small units, and each region is managed by a management data called FAT (file allocation table). When data is recorded in a region of the disk (recording medium), the FAT data is updated accordingly, and when reading out the data stored in the regions, the reading is performed based on the FAT data.
Currently, the hard disk device is disposed in the digital multifunctional device as an auxiliary memory of the semiconductor memory, considering memory capacity, price (cost of parts), and data transmission speed, and while a certain volume of job data are processed in the semiconductor memory, the newly input job data is temporarily stored in the hard disk, so that when the order for processing the new job data arrives, the data is read out onto the semiconductor memory for processing. The above configuration is provided in the market as a system for processing image data (digital multifunctional device) capable of efficiently processing a large amount of job data without delay.
However, the processing of a highly confidential document data by this type of digital multifunctional device may cause security problems. For example, the job data (image data) stored temporarily in each of the regions of the hard disk remain as data even when the job data has become unnecessary and the FAT data has been updated to store new image data, unless the newly inputted image data is overwritten on the region storing the unnecessary image data based on the FAT data, or unless the unnecessary image data remaining in the data regions are erased forcibly.
In order to overcome this drawback, Japanese Patent Laid-Open Publication No. 9-284572 discloses a system that forcibly erases the region storing the image data of the hard disk or overwrites irregular patterned images created by random numbers on the region when the processing of the image data is completed in the digital multifunctional device, so that the stored data cannot be reproduced as image.
However, strictly speaking, since the memory is composed of a magnetic storage medium, the previously stored image data is not completely impossible to read even after overwriting new image data or specific pattern on the data once, or by erasing the data.
Therefore, the present invention aims at solving the above-mentioned problems of the prior art. The object of the invention is achieved by providing an image processing device that, upon erasing the image data stored in the memory, repeats erasing operation for the regions storing the image data according to its security level so as to achieve sufficient protection of confidentiality of the image data.
Another object of the present invention is to provide an image processing device that enables the number of times of erase (erase count) to be designated from an external device corresponding to the security level of the image data when the processing of the image data is requested from the external device, in case the digital multifunctional device is equipped with a device having a communication function that enables image data to be transmitted to and received from an external device through communication. Thus, the unnecessary image data stored in the image data storage means can be erased without fail by performing erase of the image data for a number of times designated through the external device, according to which the security level of the device with respect to the image data received from the external device via the image data communication means is increased.
Yet another object of the present invention is to provide an image processing device that performs erase operation based on the preset number of times for erasing the image data set in the digital multifunctional device, and when the digital multifunctional device is equipped with a device having a communication function that enables image data to be transmitted to and received from an external device through communication, when a request for image data processing is entered through the external device, enables the erase count according to the security level of the image data to be designated through the external device, and performs erase operation by prioritizing the erase count of image data designated through the external device to the erase count of image data preset to the digital multifunctional device.